Add pagination to NewChatPage

[sharabai]

Explanation of Change

Note

#87881 must be merged first

Add pagination to NewChatPage (usePaginatedData)

Problem: Pagination used to live inside SelectionListWithSections. The screen prepared all personal details up front and the list just revealed more already-computed rows on scroll — purely visual, no real work saved. The screen had no control or visibility over it; you'd normally expect pagination at the data-preparation level, and the data flow in NewChatPage is complicated enough that it was easy to miss that pagination wasn't happening there at all. The new list doesn't carry this forward, so New Chat lost even the visual pagination while still processing the full list.

Approach: Move pagination up to the screen (NewChatPage) using a small, generic hook (usePaginatedData), applied at two points:

1. Before data preparation — cap how many raw personal details are processed (real pagination).
2. After the whole flow, before passing rows to the list, while searching — cap filtered rows (visual pagination, at the source).

Important

the two usages serve different purposes and are mutually exclusive:

• Load flow (not searching) — slice before the heavy processing so less work is done on initial open; this is the real performance win.
• Searching — the first pagination is skipped so search runs against the full dataset; instead, a purely visual pagination caps the filtered rows passed to the list. It works against already-processed data, so it doesn't affect performance — it's only there to keep the FlashList scroll from collapsing to something too small when the search result set is large.

Why: Pagination at the list level hid both work and intent. Owning it at the screen with a dedicated hook makes the data-prep flow traceable and controllable — on initial load (and whenever the user is not searching) "seeing pagination" now actually matches "pagination is happening."

Note

A purely visual pagination is still kept while the user is searching — search itself runs against the full dataset, but filtered rows are still fed into the list in chunks so the list doesn't mount everything at once.

Sort and dedupe before slicing (alphabetical pagination)

Problem: With pagination at the screen, page 1 was the first PAGINATION_SIZE of Object.values(personalDetails) — accountID order, not alphabetical. filterAndOrderOptions then alphabetized only that arbitrary slice, so loadMore could reveal a name that sorted earlier than already-visible rows. Imported phone contacts had the same issue; an Onyx-PD/contact login overlap also wasted page slots before the late dedupe in OptionsListUtils stripped one.

Approach: Dedupe + alphabetically sort the union of Onyx personal details and imported phone contacts upstream of pagination, in a small pure helper (mergeAndSortPersonalDetailsWithContacts). Dedupe key: addSMSDomainIfPhoneNumber(login).toLowerCase(). Onyx PDs are spread first, so on collision the real-accountID copy wins over the optimistic contact copy. The late personalDetails.concat(contacts) is removed (contacts are already merged upstream). While here, orderPersonalDetailsOptions is generic-ised and its sort key aligned with personalDetailsComparator, so the upstream sort agrees with the heap re-sort inside getValidOptions.

Why: A paginated slice should match the user's mental model of "first page." Sorting + deduping upstream makes page 1 the alphabetical prefix and loadMore strictly append-only under a stable data snapshot.

Performance gains on opening New Chat

With this change, opening NewChatPage on accounts with a large contact list is noticeably faster — +75.88 ms
(+22.2%) without the pagination.

Measured by forcing skipPagination: true on the first usePaginatedData usage (the one before data preparation) to simulate the previous behavior, and comparing against the current code with pagination enabled.

Fixed Issues

$ #86089
PROPOSAL:

Tests

Load-flow pagination (initial open)

1. Open the New Chat page
2. Verify the contacts list shows only a small slice (the scrollbar is short relative to the total number of contacts you know the account has)
3. Scroll to the bottom of the contacts list
4. Verify more contacts load in and the scrollbar grows, repeating as you keep scrolling

Visual pagination while searching

1. Open the New Chat page
2. Type a query in the search field that matches many contacts
3. Verify results are shown and the list is capped to a small initial slice (short scrollbar again), not the full filtered set
4. Scroll to the bottom of the search results
5. Verify more matching contacts are revealed as you scroll
6. Change the query (or clear it)
7. Verify the list resets back to its first page and pagination works again from the top

Sort + dedupe correctness

1. Open the New Chat page on an account where someone with a high accountID has an early alphabetical name (e.g. "Aaron")
2. Verify they appear on page 1, not after scrolling
3. Scroll to load more pages — already-visible rows must keep their order; new rows only append below
4. If applicable: verify a person who exists in both your phone contacts and Expensify appears exactly once (with the Onyx avatar/display name)

• Verify that no errors appear in the JS console

Offline tests

QA Steps

Same as tests

• Verify that no errors appear in the JS console

Offline tests

QA Steps

Same as tests

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
  • I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
  • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android: Native
  • Android: mWeb Chrome
  • iOS: Native
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
• I verified there are no new alerts related to the canBeMissing param for useOnyx
• I followed proper code patterns (see Reviewing the code)
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    • If any non-english text was added/modified, I used JaimeGPT to get English > Spanish translation. I then posted it in #expensify-open-source and it was approved by an internal Expensify engineer. Link to Slack message:
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• I tested other components that can be impacted by my changes (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar are working as expected)
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• I verified any variables that can be defined as constants (ie. in CONST.ts or at the top of the file that uses the constant) are defined as such
• I verified that if a function's arguments changed that all usages have also been updated correctly
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  • The file has a description of what it does and/or why is needed at the top of the file if the code is not self explanatory
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• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
• If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
• If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
  • I verified that all the inputs inside a form are aligned with each other.
  • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
• If a new page is added, I verified it's using the ScrollView component to make it scrollable when more elements are added to the page.
• I added unit tests for any new feature or bug fix in this PR to help automatically prevent regressions in this user flow.
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.

Screenshots/Videos

Android: Native

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

pagination.mp4